Cathode having an end face carrier for an emission substance and the production thereof



April 29, 1969 E HUBNER 3,441,779

CATHODEHAVING AN ENO FACE CARRIER FOR AN EMISSION SUBSTANCE AND THE PRODUCTION THEREOF Filed April 6. 1966 TTL UTLfor: Erwin. Hbnve r @wil d@ United States Patent O CATHODE HAVING AN END FACE CARRIER FOR AN EMISSION SUBSTANCE AND THE PRODUC- TION THEREOF Erwin Hbner, Munich, Germany, assignor to Siemens Aktiengesellschaft, Munich, Germany, a corporation of Germany Filed Apr. 6, 1966, Ser. No. 540,576

Int. Cl. H01j 1/14 U.S. Cl. 313-346 4 Claims ABSTRACT F THE DISCLOSURE A large-surface emitting cathode with a front-side emission substance carrier plate and a construction including two telescoped construction groups, the outer construction group comprising a mushroom-shaped cathode carrier, the emission material carrier plate being soldered or welded to the flange-like end of said cathode carrier, and the inner construction group being telescoped into the single opening of the outer construction group and comprises a sheet metal cylinder as a storage tank having a sealed bottom substantially curved inwardly and being welded at the bottom edge so that its tined upper edge bears against the emission material carrier plate.

The invention relates to a cathode for electrical discharge vessels having an end face formed by a porous carrier plate, for the emission substance, which is constructed of a high-melting metal, such as tungsten or the like, and covers a supply which, in operation, gives olf emission-promoting substances, in which such carrier plate, if of a nominal thickness of about 0.6 mm., has a diameter greater than 3 mm. or else is of especially thin construction, whereby the ratio of diameter of thickness is relatively great.

Such cathodes are used, `in particular, in cathode beam tubes of all -knds as well as in disk tubes and traveling wave tubes in the highest-frequency field. In cathodes with a diameter of the carrier plate for the emission substance greater than 3 mm. it is found that in operation there takes place a more or less severe deformation or pancaking of the carrier plate for the emission substance, which expresses itself in a curvature of the plate inward toward the supply and thus alters the operational geometry and, as a consequence, also the operational characteristics interrelated therewith. The degree of deformation depends on the diameter and the thickness of the porous carrier plate for the emission substance of such cathode and, above all, also on the height of the heating temperature to be utilized in operation. In the production of the porous carrier plate for the emission substance, however, it is possible to take certain countersteps against this phenomenon only to a limited extent through suitable measures, as, for example, through special selection of the compression prssure, the grain size and the sintering temperature.

On the other hand, failure of cathodes can also occur through the fact that the permeability of the porous carrier plate for the emission substance has become, for example, too great or too uneven after its attachment to the cathode carrier, especially if by soldering or arc welding. Likewise, the heating to soldering or welding temperature, especially in the assembly of the cathode, can so damage the supply substance, especially by distintegrating, that it no longer is capable of full efficiency after the cathode in question has been placed in operation with respect to its function of conducting the emission substance.

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The problem underlying the invention involves, therefore, the avoidance of, through special constructive formation of the cathode and its individual parts, the disturban'ces occurring in the assembling of such cathodes embodying the prior constructions commonly employed or subsequently appearing only in operation, without disadvantageously influencing or changing the determinative characteristic magnitudes and operation of the discharge vessel concerned.

This is achieved according to the invention, in a cathode as initially described for electrical discharge vessels having an end face formed as a porous carrier for the emission substance, by a construction utilizing at least two structural groups or subassemblies, one of which is insertable into the other. The outer subassembly comprises a generally mushroom-shaped cathode carrier having a central bore therethrough, which carries the porous carrier plate, the cathode heater and an outer radiation shell, with the heater being cemented in place between the outer shell and the adjacent portion of the cathode carrier. The inner subassembly comprises a sheet metal cylinder, closed at its lower end to form the supply container for the emission substance, the cylinder being provided with openings or notches in its opposite end. In the assembly of the two completed assemblies, the cylinder is inserted into said central bore with said opposite end engaging the inner face of the carrier plate for the emission substance and is then secured at its closed end to the cathode carrier.

Further details of the invention will be explained with the aid of an example of construction purely schematically illustrated in the drawing.

The reference numeral 1 designates a generally mushroom-shaped carrier having a continuous central bore 2 therein, along which it is relatively thick-walled, and is provided on its end face with a flange 4 of relatively large diameter for the attachment of the carrier plate 3 for the porous emission substance. The securement of the carrier plate for the emission substance may be accomplished by soldering or arc welding. To assure a uniform distribution of the emission-promoting substances, there is formed underneath the carrier plate or disk 3 for the emission substance, a shallow cylindrical space 5 of somewhat smaller diameter than that of the carrier plate. Disposed at the outer circumference of the cathode carrier, below the flange 4, is a heater 6 in the form of an insulated spiral which is cemented thereto and enclosed by a sheet metal sleeve or shell 7, which, in turn, is surrounded by a radiation protective shield 8, for example, in the form of a foil cylinder. The parts 1 to 8 thus far described represent one of two structural groups or subassemblies, namely, the outer structures. The other, second, inner structural subassembly or group comprises the supply container proper, in the form of a sheet metal cylinder 9 which is closed at its lower end by an inwardly domed cylinder 10 which may be sealed, for example, by arc welding. At its upper end the sheet metal cylinder is suitably formed, as for example, in such a way that wall portions 12 remain between openings or notches 11. Upon the insertion of the supply container 9 as the one structural group into the other structural group, the ends of the wall portions 12 will contact the porous carrier plate for the emission substance whereby such carrier plate is centrally supported with certainty and thus cannot sag in operation as a result of thermal loading. The two structural groups inserted one into the other may be tightly joined at their edges, for example, by arc welding.

The particular advantage of a supply cathode construction consisting of at least two structural units, as compared to constructions heretofore employed, resides above all in the fact that an Operational testing, especially a determination of permeability of the porous carrier plate for the emission substance, can be effected, following attachment thereof to the cathode carrier, at the last moment, so to speak, before the final assembly, whereby it is possible to detect flaws which may have occurred in the assembly of a structural group, for example, in the welding and soldering process. Moreover, the porous carrier plate for the emission substance can still be subsequently coated with any suitable material, for example, aluminum oxide, which has the particular advantage of requiring no heating in addition to that employed in the initial operation of the cathode involved. Obviously, other parts in the individual structural groups can be tested prior to assembly, such as, for example, the very important insulation of the heater.

The broadest freedom in the selection of the supply substance is achieved through the special construction of the inner structural group, as the rather deeply inset base closure within the supply container proper prevents the occurrence of a troublesome heating of the supply substance in the assembling operations. The supply itself can be introduced as a loose powder, as pellets, or, if necessary, can be molded or pressed therein. Of particular importance in the cathode described is that absolute assurance that the porous carrier plate for the emission substance is eectively centrally supported, whereby no sagging thereof can occur in operation.

Changes may be made within the scope and spirit of the appended claims which define what is believed to be new and desired to have protected by Letters Patent.

I claim:

1. A cathode, for use in electrical discharge vessels, provided with a porous end face in the form of a carrier plate for an emission substance, which plate is formed from a high-melting metal, such as tungsten or the like, and covers a supply of substances which will promote emission during operation, in which the ratio of diameter to thickness of the plate is relatively large, comprising at least two structural subassemblies, one of which comprises a generally mushroom-shaped cathode body having a central bore extending therethrough, such porous carrier plate for the emission material being secured to said cathode body at the enlarged end thereof, and forming an end face therefor, and outer radiation protective shell disposed adjacent the smaller portion of said body, a heater disposed between said shell and said body, and secured to said body, and another structural assembly comprising a container, for the supply of an emission substance in the form of a sheet metal cylinder, said cylinder being closed at one end and open at its other end and having openings in the side walls at its said other end for the passage of emission substance, said second structural subassembly being disposed in said central bore of the cathode body with said other open end of the cylinder in engagement with and supporting said carrier plate to provide a reinforcement therefor, the closed end of said second subassembly being rigidly connected to said cathode body.

2. A cathode according to claim 1, wherein the sheet metal cylinder forming the supply container is closed at the outer edge thereof with a cylindrical sheet metal cap inset considerably inwardly into the cylinder and secured thereto.

3. A cathode according to claim 1, wherein the mushroom-shaped cathode carrier is constructed of a material having good heat stability, and is relatively very thickwalled,

4. A cathode according to claim 1, wherein said open end of said sheet metal cylinder includes a plurality of tines for supporting said carrier plate circumferentially disposed about the open end of said cylinder and an individual slot between adjacent ones of said tines forming said openings for the passage of said emission substance.

References Cited UNITED STATES PATENTS 2,433,813 12/1947 Hilliard 313-240 X 2,761,993 9/ 1956 Katz et al 313-3 37 X 2,774,916 12/1956 Katz 313-346 X 3,010,046 11/1961 Dailey et al. 313-346 FOREIGN PATENTS 1,112,209 8/1961 Germany. 1,132,256 6/1962 Germany. 1,182,355 11/1964 Germany.

JOHN W. HUCKERT, Primary Examiner.

A. J. JAMES, Assistant Examiner.

U.S. Cl. X.R. 313-337, 339 

